Process for converting methanol to olefins

Abstract

There is provided a process for converting methanol or dimethyl ether to a product containing C 2 to C 4 olefins, which comprises the step of contacting a feed containing methanol or dimethyl ether with a catalyst which comprises a zeolite having 10-ring intersecting channels, such as ZSM-5, and which has a Diffusion Parameter for 2,2-dimethylbutane of less than 100 sec −1 when measured at a temperature of 120° C. and a 2,2-dimethylbutane pressure of 60 torr (8 kPa). The contacting step is conducted at a temperature of 370 to 480° C., a methanol partial pressure of 30 to 150 psia and a methanol conversion per pass of less than 95%.

What is claimed is:  
     
       1. A process for converting methanol or dimethyl ether to a product containing C 2  olefin, the process comprising the step of contacting a feed containing methanol or dimethyl ether and an aromatic compound which has a critical diameter less than the pore size of the zeolite catalyst and which is capable of alkylation by the methanol and/or dimethyl ether with a catalyst which comprises a zeolite having 10-ring intersecting channels and which has a Diffusion Parameter for 2,2-dimethylbutane of less than 100 sec −1  when measured at a temperature of 120° C. and a 2,2-dimethylbutane pressure of 60 torr, the contacting step being conducted at a temperature of 370 to 480° C., a methanol or dimethyl partial pressure of 30 to 150 psia to provide C 2  olefin. 
     
     
       2. The process of  claim 1 , wherein said Diffusion Parameter of said catalyst is about 0.1-30 sec −1 . 
     
     
       3. The process of  claim 1 , wherein said contacting step is conducted at a temperature of 400 to 450° C. and a methanol or dimethylether partial pressure of 60 to 120 psia. 
     
     
       4. The process of  claim 1 , wherein said contacting step is conducted such that methanol or dimethylether conversion per pass is less than 95%. 
     
     
       5. The process of  claim 1 , wherein said methanol or dimethylether conversion per pass is 25-90%. 
     
     
       6. The process of  claim 1 , wherein said catalyst contains an oxide of phosphorus. 
     
     
       7. The process of  claim 1 , wherein said catalyst contains about 0.05 to about 20 wt % of an oxide of phosphorus on an elemental basis. 
     
     
       8. The process of  claim 1 , wherein said zeolite is ZSM-5 or ZSM-11.